The disclosure generally relates to adaptive filters.
In many communication devices, the receiver circuit often utilizes the adaptive filter to equalize the interferences brought by the channel effects and therefore may recover the signals sent by the transmitter. In some applications, complicated adaptive filters are required to effectively equalize the channel effects. For example, in the Advanced Television Systems Committee (ATSC) digital television system, the receiver circuit usually requires an adaptive filter with hundreds or even thousands of taps.
As the length of the adaptive filter (i.e., the number of taps of the adaptive filter) increases, the adaptive filters must be equipped with a large memory and more computation circuits to generate the filter outputs and to update the equalization parameters of the adaptive filter circuits. Accordingly, the hardware requirement and the computation complexity of the adaptive filter increase, and the accompanied increase of the power consumption also result in the heat dissipation problem. The complexity of designing and integrating the adaptive filter with a long filter length in the system is inevitably increased.
On the other hand, shortening the length of the adaptive filter usually degrades the demodulation performance of the receiver circuit. The receiver circuit may not even successfully demodulate the received signals when the channel varies dramatically. Thus, it is not feasible to simply shorten the length of the adaptive filter for reducing the hardware requirement and the computation complexity of the receiver circuit.